Abstract: A ladder locking device used for securing ladders on truck and van racks with the ability to tighten and lock the ladder in place, providing safety and theft deterrent for the consumer. The ladder locking device includes a handle, a hook, and a locking arm assembly including a hook, and a threaded key mechanism. The hook accommodates a ladder rack. The handle can include a threaded tightening shaft which rotates through a threaded tightening shaft receiver in the locking arm assembly, moving the locking arm assembly hook against a ladder rung. The locking arm assembly can be extended to accommodate up to five ladders. A key is inserted into and rotates the threaded key mechanism, thus rotating a threaded shaft attached to the threaded key mechanism. Locking pins within the ladder locking device are then pushed downward by spring mechanisms and by the threaded shaft. The locking pins then extend through holes in the locking arm assembly, locking the locking arm assembly in place.